Integrated seismic inversion for clastic reservoir characterization: Case of the upper Silurian reservoir, Tunisian Ghadames Basin.

Deltaic petroleum systems are often complex and heterogeneous. Delineation of sandstone bodies in such complex depositional settings constitutes a crucial challenge in reservoir exploration. However, reservoir characterization based on conventional well-logs and stratigraphic interpretation in complex settings often leads to uncertainties. In this work, we present an integrated quantitative interpretation to reveal heterogeneity and the reservoir properties in a complex deltaic environment. The study benefits from integrating borehole lithology logs, electrical well logging, and a 3D post-stack seismic cube. To demonstrate the practical application and effectiveness of our proposed approach, seismic inversion has been applied to the Acacus Formation in the Ghadames Basin of southern Tunisia. We estimate the acoustic impedance volume from 3D seismic data using a stochastic inversion algorithm. This algorithm enables the generation of multiple realizations, accounting for uncertainties and providing a more comprehensive understanding of subsurface impedance. Then, the porosity model is computed by establishing a functional relationship between acoustic impedance and porosity. The analysis of the relationship between acoustic impedance and different rock properties helped to differentiate lithological units of sandstone and claystone. This lithology classification is used to estimate the lithofacies model. Finally, the obtained porosity and lithofacies models are validated with well data. The crucial correlation between facies distribution and porosity allows for accurate mapping of individual thin sandstone bodies and their property distribution beyond well control. The lithofacies model shows significant sandstone bodies in the Acacus A and C units that constitute good reservoirs. The porosity model confirms this, as these sandstone facies exhibit high porosity (20%). The proposed approach has proven to be powerful in reservoir delineation, characterization, and exploration, and can be applied in similar geological setting basins, and frameworks. • Acoustic impedance volume is estimated from seismic data using a stochastic inversion algorithm. • Acoustic impedance's relationship with different rock properties is analyzed, for sandstone and claystone differentiation. • Porosity cube is obtained from a linear relationship with acoustic impedance. • Lithofacies model is derived from a lithological classification using acoustic impedance cross-plot versus VpVs ratio. • Heterogeneity and reservoir characteristics of the Acacus sandstone are revealed based on an integrated interpretation. [ABSTRACT FROM AUTHOR]